Technical Field
The present invention relates to a wrench catching device driven in a single direction, characterized in that the catching device has two catches operating in the same direction.
Description of Related Art
Wrenching tools nowadays are sophisticated. Among them, a one-way wrench structure is simple and durable, as its structure is characterized mostly in that: a driving element for use with a ratchet wheel is disposed in a driving hole; and the driving element is externally provided with ratchet teeth operating in conjunction with a catching device. However, the number of ratchet teeth is subjected to a strength-related limit, i.e., a maximum of 72. That is to say, in the situation where the driving element has more than 72 ratchet teeth, each of the ratchet teeth is overly small; as a result, not only are the ratchet teeth incapable of transmitting a driving force exerted thereon, but the ratchet teeth are also likely to get damaged. Hence, the driving element has a minimum tooth-changing angle of 5° approximately. Due to the aforesaid limitation, the wrench fails to work in a driving operation environment where the tooth-changing angle is less than 5°.
To address the aforesaid issue, wrench manufacturers develop a catching device with two catches, which is shown in FIG. 1 and characterized in that: a driving hole 11 is disposed in a wrench body 10 and adapted to receive a driving element 20; the driving hole 11 is flanked by two catching chambers 12; two catching devices A each have a catch 30 and a position-restoring element 40 which get engaged with the driving element 20 at different timing to effectuate engagement by increasing the number of ratchet teeth twofold and reduce the transmission-oriented tooth-changing angle by 50%, such that a wrench with the catching device can operate in circumstances which require a small transmission-oriented tooth-changing angle. However, the aforesaid structure necessitates the two catching chambers 12 and thus renders its operation intricate. Furthermore, one end of each of the position-restoring elements 40 of the two catching devices A abuts against the catches 30, whereas the other end of each of the position-restoring elements 40 of the two catching devices A abuts against the curved wall of the catching chambers 12. The catching chambers 12 are curved and increasingly shallower. The position-restoring elements 40 are capable of thrusting resiliently to thereby move spontaneously toward the shallower ends of the catching chambers 12 and even end up in the gap between the catching chamber 12 and the driving element 20, thereby causing the driving element 20 to get stuck. Therefore, there is still room for improvement of the prior art.